selftests/bpf: Reject graph kptr use after RCU unlockgrafted

Add a sleepable verifier test that loads a graph-node local kptr in an
explicit RCU read-side critical section, then passes its node to
bpf_rbtree_remove() after the section ends.

Before the verifier fix, the stale NON_OWN_REF flag makes the node look like
a live borrowed reference and the program is accepted. After the fix, the
pointer is demoted without NON_OWN_REF and the graph kfunc argument is
rejected.

Also exercise a graph kptr loaded while a spin lock provides implicit RCU
protection. The pointer must be invalidated when the lock is released, which
guards the required ordering between non-owning-reference invalidation and
RCU demotion.

Update the existing fault-protected load test state description. The
post-unlock pointer no longer carries NON_OWN_REF, but remains readable
because the load is rewritten to use BPF_PROBE_MEM.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 174 insertions, 0 deletions

diff --git a/drivers/mfd/88pm860x-i2c.c b/drivers/mfd/88pm860x-i2c.c
new file mode 100644
index 000000000..a000aed35
--- /dev/null
+++ b/drivers/mfd/88pm860x-i2c.c
@@ -0,0 +1,174 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * I2C driver for Marvell 88PM860x
+ *
+ * Copyright (C) 2009 Marvell International Ltd.
+ *
+ * Author: Haojian Zhuang <haojian.zhuang@marvell.com>
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/regmap.h>
+#include <linux/mfd/88pm860x.h>
+
+int pm860x_reg_read(struct i2c_client *i2c, int reg)
+{
+	struct pm860x_chip *chip = i2c_get_clientdata(i2c);
+	struct regmap *map = (i2c == chip->client) ? chip->regmap
+				: chip->regmap_companion;
+	unsigned int data;
+	int ret;
+
+	ret = regmap_read(map, reg, &data);
+	if (ret < 0)
+		return ret;
+	else
+		return (int)data;
+}
+EXPORT_SYMBOL(pm860x_reg_read);
+
+int pm860x_reg_write(struct i2c_client *i2c, int reg,
+		     unsigned char data)
+{
+	struct pm860x_chip *chip = i2c_get_clientdata(i2c);
+	struct regmap *map = (i2c == chip->client) ? chip->regmap
+				: chip->regmap_companion;
+	int ret;
+
+	ret = regmap_write(map, reg, data);
+	return ret;
+}
+EXPORT_SYMBOL(pm860x_reg_write);
+
+int pm860x_bulk_read(struct i2c_client *i2c, int reg,
+		     int count, unsigned char *buf)
+{
+	struct pm860x_chip *chip = i2c_get_clientdata(i2c);
+	struct regmap *map = (i2c == chip->client) ? chip->regmap
+				: chip->regmap_companion;
+	int ret;
+
+	ret = regmap_raw_read(map, reg, buf, count);
+	return ret;
+}
+EXPORT_SYMBOL(pm860x_bulk_read);
+
+int pm860x_bulk_write(struct i2c_client *i2c, int reg,
+		      int count, unsigned char *buf)
+{
+	struct pm860x_chip *chip = i2c_get_clientdata(i2c);
+	struct regmap *map = (i2c == chip->client) ? chip->regmap
+				: chip->regmap_companion;
+	int ret;
+
+	ret = regmap_raw_write(map, reg, buf, count);
+	return ret;
+}
+EXPORT_SYMBOL(pm860x_bulk_write);
+
+int pm860x_set_bits(struct i2c_client *i2c, int reg,
+		    unsigned char mask, unsigned char data)
+{
+	struct pm860x_chip *chip = i2c_get_clientdata(i2c);
+	struct regmap *map = (i2c == chip->client) ? chip->regmap
+				: chip->regmap_companion;
+	int ret;
+
+	ret = regmap_update_bits(map, reg, mask, data);
+	return ret;
+}
+EXPORT_SYMBOL(pm860x_set_bits);
+
+static int read_device(struct i2c_client *i2c, int reg,
+		       int bytes, void *dest)
+{
+	unsigned char msgbuf0[I2C_SMBUS_BLOCK_MAX + 3];
+	unsigned char msgbuf1[I2C_SMBUS_BLOCK_MAX + 2];
+	struct i2c_adapter *adap = i2c->adapter;
+	struct i2c_msg msg[2] = {
+					{
+						.addr = i2c->addr,
+						.flags = 0,
+						.len = 1,
+						.buf = msgbuf0
+					},
+					{	.addr = i2c->addr,
+						.flags = I2C_M_RD,
+						.len = 0,
+						.buf = msgbuf1
+					},
+				};
+	int num = 1, ret = 0;
+
+	if (dest == NULL)
+		return -EINVAL;
+	msgbuf0[0] = (unsigned char)reg;	/* command */
+	msg[1].len = bytes;
+
+	/* if data needs to read back, num should be 2 */
+	if (bytes > 0)
+		num = 2;
+	ret = adap->algo->master_xfer(adap, msg, num);
+	memcpy(dest, msgbuf1, bytes);
+	if (ret < 0)
+		return ret;
+	return 0;
+}
+
+static int write_device(struct i2c_client *i2c, int reg,
+			int bytes, void *src)
+{
+	unsigned char buf[2];
+	struct i2c_adapter *adap = i2c->adapter;
+	struct i2c_msg msg;
+	int ret;
+
+	buf[0] = (unsigned char)reg;
+	memcpy(&buf[1], src, bytes);
+	msg.addr = i2c->addr;
+	msg.flags = 0;
+	msg.len = bytes + 1;
+	msg.buf = buf;
+
+	ret = adap->algo->master_xfer(adap, &msg, 1);
+	if (ret < 0)
+		return ret;
+	return 0;
+}
+
+int pm860x_page_reg_write(struct i2c_client *i2c, int reg,
+			  unsigned char data)
+{
+	unsigned char zero;
+	int ret;
+
+	i2c_lock_bus(i2c->adapter, I2C_LOCK_SEGMENT);
+	read_device(i2c, 0xFA, 0, &zero);
+	read_device(i2c, 0xFB, 0, &zero);
+	read_device(i2c, 0xFF, 0, &zero);
+	ret = write_device(i2c, reg, 1, &data);
+	read_device(i2c, 0xFE, 0, &zero);
+	read_device(i2c, 0xFC, 0, &zero);
+	i2c_unlock_bus(i2c->adapter, I2C_LOCK_SEGMENT);
+	return ret;
+}
+EXPORT_SYMBOL(pm860x_page_reg_write);
+
+int pm860x_page_bulk_read(struct i2c_client *i2c, int reg,
+			  int count, unsigned char *buf)
+{
+	unsigned char zero = 0;
+	int ret;
+
+	i2c_lock_bus(i2c->adapter, I2C_LOCK_SEGMENT);
+	read_device(i2c, 0xfa, 0, &zero);
+	read_device(i2c, 0xfb, 0, &zero);
+	read_device(i2c, 0xff, 0, &zero);
+	ret = read_device(i2c, reg, count, buf);
+	read_device(i2c, 0xFE, 0, &zero);
+	read_device(i2c, 0xFC, 0, &zero);
+	i2c_unlock_bus(i2c->adapter, I2C_LOCK_SEGMENT);
+	return ret;
+}
+EXPORT_SYMBOL(pm860x_page_bulk_read);